1. Field of the Invention
The present invention relates to a clamshell type copying machine in which an upper body and a lower body are rotatably connected with each other at ends thereof and can be opened at the other ends thereof.
2. Description of the Related Art
In an electrophotograph copying machine, one of clamshell type copying machines, an upper body and a lower body are rotatably connected with each other via a damper at ends thereof and can be opened at the other ends thereof. The damper reduces the impact generated when the upper body is opened against the lower body, and allows a user to more readily open the upper body readily.
In such a copying machine, an original cover is mounted on an original plate (glass plate) of the upper body so that it can be opened. For the copying operation, the original cover is opened, and then a document to be copied is set on the original plate. Then, the original cover is closed on the original plate so as to hold the document in place.
However, in the case where a number of documents are to be copied with such a copying machine, much manual operation is required in changing and handling the documents. Therefore, an automatic document feeder (ADF) is generally substituted for the original cover so as to automatically feed the documents onto the original plate. In order to use the ADF, the original cover is removed from the upper body of the copying machine. That is, the original cover and the ADF are selectably mounted on the original plate so as to be replaced with each other.
The ADF comprises rollers, gears, a motor and the like for successively feeding the documents onto the original plate, so that the weight of the ADF is much heavier than that of the original cover. As a result, in the case where the ADF. is mounted on the upper body, the damper cannot sufficiently reduce the impact generated when the upper body is opened against the lower body, and much force is required for the opening.
Japanese Laid-Open Utility Model Publication No. 59-141345 and Japanese Laid-Open Patent Publication No. 60-42769 disclose a copying machine in which the position of a damper is adjusted when an ADF is mounted on an upper body of the copying machine so as to tolerate the weight of the ADF. However, this copying machine has a disadvantage in that additional operations are required for adjusting the position of the damper.
Japanese Laid-Open Utility Model Publication No. 57-49246 discloses a copying machine in which the weight of an original cover is increased up to the weight of an ADF so as to balance the former with the latter. However, this copying machine also has a disadvantage in that it is not easy to handle such a heavy original cover.
Furthermore, there is proposed a method in which a damper is replaced with another one when an original cover is replaced with an ADF. However, this method also has a disadvantage in that additional operations are required for replacing the damper with another one.